1. Field of the Invention
The present invention relates to a lens barrel of a camera, and in particular relates to a lens barrel of a camera which includes a flexible printed wiring board used for establishing electrical connections between one or more electronic components installed in the lens barrel and another component or components installed in the lens barrel or the camera body to which the lens barrel is mounted.
2. Description of the Related Art
To install electronic components such as an electromagnetic diaphragm and various sensors in a lens barrel of an SLR camera, such as a standard lens or an interchangeable lens, a flexible PWB (printed wiring board) is often used to establish electrical connections between such electronic components and, e.g., a stationary board such as a stationary circuit board provided in the camera body. In this type of lens barrel, it is occasionally the case that the positions of such electronic components in the lens barrel are required to be adjusted in the lens barrel, so that the flexible PWB is arranged to be flexibly extendable in a bent state inside the lens barrel to allow the electronic components to move inside of the lens barrel. Namely, the flexible PWB is elastically deformed to be straightened when the electronic components are fully moved to the maximum in one direction and bent when the electronic components are fully moved to the maximum in the opposite direction, which makes it possible to adjust the positions of the electronic components while ensuring electrical connections between the electronic components and the flexible PWB regardless of the movements of the electronic components. However, if the flexible PWB is bent in such a manner, a bent portion of the flexible PWB may be deformed in a radial direction of the lens barrel so as to interfere with adjacent internal components of the lens barrel, including optical elements, thus impeding normal operations of these internal components of the lens barrel. In addition, such interference of the bent portion of the flexible PWB with adjacent internal components of the lens barrel causes faulty electrical signals to be produced due to mechanical and electrical factors.
To overcome such problems, Japanese unexamined patent publication H07-168077 discloses a lens barrel structure in which a flexible PWB is connected to a vibration sensor installed in the lens barrel, wherein the flexible PWB is installed in a cutout portion on an internal wall of the lens barrel to have an arch shape which does not interfere with the vibration sensor. This configuration makes it possible to adjust the position of the vibration sensor while preventing the flexible PWB from interfering with the vibration sensor, which resolves the aforementioned production of faulty electrical signals due to mechanical and electrical factors, e.g., due to vibrations of the flexible PWB.
In the technique of installing a flexible PWB in a lens barrel with the flexible PWB being bent in a manner as shown in the aforementioned Japanese unexamined patent publication, the amount of bending of the flexible PWB increases by bending stress applied to the flexible PWB. However, the portion of the flexible PWB whose amount of bending increases depends on the shape, dimensions or the initial bending state of the flexible PWB, and is therefore difficult to determine uniquely, and accordingly, it is impossible to predict the portion of the flexible PWB that will interfere with internal components of the lens barrel. Therefore, in the prior art, a margin of clearance between the flexible PWB and the internal components of the lens barrel needs to be provided so that no interference occurs therebetween even if the amount of bending of the flexible PWB increases at any point thereon, and it is conventionally difficult to miniaturize the lens barrel by this margin.